The present invention relates to a bulky sheet material having a large number of three-dimensional protrusions and showing an elastomeric behavior as a whole and breathability.
The subject in developing absorbent articles such as sanitary napkins and disposable diapers is fulfillment of requirements that: absorbent articles should retain wastes discharged from the body such as menstrual blood and urine without leakage; brought into direct contact with a wearer's skin, they should not give a wearer discomfort; and they should not cause a rash due to overhydration and the like.
Conventional absorbent articles are not easily deformable even with pressure applied while worn and therefore give a wearer discomfort. They are incapable of following the wearer's contour or movement, tending to result in leakage. The wearer's side having a smooth surface and being made of a relatively high-density material, they are liable to cause a skin rash due to overhydration.
To eliminate these inconveniences, JP-A-6-128853 proposes using wrinkly nonwoven fabric as a topsheet of an absorbent article. The wrinkly nonwoven fabric disclosed exhibits insufficient recovery when extended in the planar direction. Therefore, where used as a topsheet, etc. of an absorbent article, it has insufficient conformability to the movement of a wearer, tending to result in a leak. Besides, the wrinkly nonwoven fabric has insufficient compressive deformability when compressed in its thickness direction. Therefore, when it is deformed by compression while worn, it is liable to come into intimate contact with the wearer's body to give discomfort.
JP-A-62-141167 teaches a method of making a composite sheet having an uneven structure, which comprises superposing nonwoven sheets having different shrinkages on each other and joining them in parts. Similarly to the aforementioned wrinkly nonwoven fabric, the composite sheet is unsatisfactory in recovery from extension in the planar direction and deformability when compressed in the thickness direction. Moreover, because knitted fabric is used as a sheet having a smaller thermal shrinkage, the composite sheet as a whole has a high density, which can cause overhydration.
JP-A-9-111631 discloses a wrinkled nonwoven fabric comprising a first fibrous layer and a second fibrous layer provided on one side of the first fibrous layer in which the first fibrous layer contains thermally shrinkable fibers and the second fibrous layer contains thermally fusible fibers. Two fibrous layers are combined in the thickness direction at the thermally bonded portions of linear shape. The thermally bonded portions form recessed regions and the portions between the thermally bonded portions form raised regions. In addition, the second fibrous layers has a great number of wrinkles of linear shape. This wrinkled nonwoven fabric, however, is unsatisfactory in recovery from extension in the planar direction and deformability when compressed in the thickness direction.